In current semiconductor industry, electronic packaging has become an important aspect in the development of the industry. After decades of packaging technology development, conventional peripheral-wiring-type packaging method and ball grid array packaging technology can no longer meet current high-density and small-size packaging requirements. Wafer-level chip scale packaging technology (WLCSP) has become a popular packaging method.
FIG. 1 depicts a cross-sectional view of a packaging structure of an existing WLCSP method. The structure includes a silicon substrate 1, an insulating layer 2 on a surface of the silicon substrate 1. The insulating layer 2 has an opening. The surface of the silicon substrate 1 exposed by the opening has a pad 3. A rewiring metal layer 4 is disposed on the pad 3 and a surface of the insulating layer 2. The rewiring metal layer 4 is used for redistributing positions of ball grid array packaging solder joints. A copper pillar 5 is formed on a surface of the rewiring metal layer 4. The copper pillar 5 is connected to the pad 3 via the rewiring metal layer 4. A sealing material layer 6 made of organic resin is disposed to cover the rewiring metal layer 4 and the insulating layer 2. A solder ball 7 is formed on the top surface of the copper pillar 5.
However, the solder ball 7 as described in the above packaging structure can easily fall off from the top surface of the copper pillar 5 and, as a result, cause chip failure.